Method and apparatus for accessing legacy networks through temporary ID of evolved network

Abstract

In a method for accessing a legacy wireless network, a radio access network (RAN) node in the legacy wireless network receives an access message sent by a User Equipment (UE) attempting to access the legacy wireless network. The access message includes mobility management entity (MME) information identifying an MME accessed by the UE in an evolved network. The MME information is added by the UE from a temporary identity (ID) allocated by the MME to a first P-Temporary Mobile Station Identity (P-TMSI) in the access message. The RAN node selects a corresponding Serving GPRS Support Node (SGSN) in the legacy wireless network for the UE according to the first P-TMSI in the access message.

The invention claimed is: 
     
       1. A method for retrieving User Equipment (UE) context, the method comprising:
 receiving, by a Mobility Management Entity (MME) in an evolved network, a Routing Area Identification (RAI), a P-Temporary Mobile Station Identity (P-TMSI) and a P-TMSI signature from a Serving GPRS Support Node (SGSN) in a 2G/3G network, wherein the RAI, P-TMSI and P-TMSI signature are mapped from a temporary identity (ID) for identifying a UE in the evolved network; 
 obtaining, by the MME, the temporary ID according to the RAI, P-TMSI and P-TMSI signature; and 
 returning, by the MME, a UE context corresponding to the UE according to the obtained temporary ID. 
 
     
     
       2. The method of  claim 1 , wherein an MME-Identity (MME-id) for identifying an MME within a pool is mapped from the temporary ID to the P-TMSI. 
     
     
       3. The method of  claim 2 , wherein the MME-id is mapped from the temporary ID to a Network Resource Identifier (NRI) field of the P-TMSI. 
     
     
       4. The method of  claim 3 , wherein a pool-id for identifying a pool the MME belongs to is mapped from the temporary ID to a Location Area Code (LAC) field of the RAI. 
     
     
       5. The method of  claim 4 , wherein a Public Land Mobile Network-Identity (PLMN-id) from the temporary ID is mapped to a Mobile Country Code (MCC) field and a Mobile Network Code (MNC) field of the RAI. 
     
     
       6. The method of  claim 5 , wherein an M-TMSI from the temporary ID is mapped to the P-TMSI and the P-TMSI Signature. 
     
     
       7. The method of  claim 6 , wherein the MME-id is further mapped from the temporary ID to a Routing Area Code (RAC) field of the RAI. 
     
     
       8. The method of  claim 1 , wherein the temporary ID is an SAE-TMSI, wherein the SAE-TMSI is longer than the P-TMSI. 
     
     
       9. A network equipment, comprising:
 a receiver configured to receive a Routing Area Identification (RAI), a P-Temporary Mobile Station Identity (P-TMSI) and a P-TMSI signature from a Serving GPRS Support Node (SGSN) in a 2G/3G network, wherein the RAI, P-TMSI and P-TMSI signature are mapped from a temporary identity (ID) for identifying a User Equipment (UE) in an evolved network; and 
 a processor configured to obtain the temporary ID according to the RAI, P-TMSI and P-TMSI signature, and return a UE context corresponding to the UE according to the obtained temporary ID. 
 
     
     
       10. The network equipment of  claim 9 , wherein an MME-Identity (MME-id) for identifying a Mobility Management Entity (MME) within a pool is mapped from the temporary ID to a Network Resource Identifier (NRI) field of the P-TMSI. 
     
     
       11. The network equipment of  claim 10 , wherein a pool-id for identifying a pool the MME belongs to is mapped from the temporary ID to a Location Area Code (LAC) field of the RAI. 
     
     
       12. The network equipment of  claim 11 , wherein a Public Land Mobile Network-Identity (PLMN-id) from the temporary ID is mapped to a Mobile Country Code (MCC) field and a Mobile Network Code (MNC) field of the RAI. 
     
     
       13. The network equipment of  claim 12 , wherein an M-TMSI from the temporary ID is mapped to the P-TMSI and the P-TMSI Signature. 
     
     
       14. The network equipment of  claim 9 , wherein the temporary ID is an SAE-TMSI, wherein the SAE-TMSI is longer than the P-TMSI. 
     
     
       15. A communication system, comprising: a Mobility Management Entity (MME) in an evolved network and a Serving GPRS Support Node (SGSN) in a 2G/3G network,
 wherein the SGSN is configured to send a Routing Area Identification (RAI), a P-Temporary Mobile Station Identity (P-TMSI) and a P-TMSI signature to the MME, and the RAI, P-TMSI and P-TMSI signature are mapped from a temporary identity (ID) for identifying a User Equipment (UE) in the evolved network; and 
 the MME is configured to receive the RAI, P-TMSI and P-TMSI signature, to obtain the temporary ID according to the RAI, P-TMSI and P-TMSI signature, and to return a UE context corresponding to the UE according to the obtained temporary ID. 
 
     
     
       16. The communication system of  claim 15 , wherein an MME-Identity (MME-id) for identifying a Mobility Management Entity (MME) within a pool is mapped from the temporary ID to a Network Resource Identifier (NRI) field of the P-TMSI. 
     
     
       17. The communication system of  claim 16 , wherein a pool-id for identifying a pool the MME belongs to is mapped from the temporary ID to a Location Area Code (LAC) field of the RAI. 
     
     
       18. The communication system of  claim 17 , wherein a Public Land Mobile Network-Identity (PLMN-id) from the temporary ID is mapped to a Mobile Country Code (MCC) field and a Mobile Network Code (MNC) field of the RAI. 
     
     
       19. The communication system of  claim 18 , wherein an M-TMSI from the temporary ID is mapped to the P-TMSI and the P-TMSI Signature. 
     
     
       20. The communication system of  claim 15 , wherein the temporary ID is an SAE-TMSI, wherein the SAE-TMSI is longer than the P-TMSI.